Methods for preparing nanotextured surfaces and applications thereof

ABSTRACT

A rapid and inexpensive technique for generating nanotextured surfaces is disclosed. The technique involves the (1) creation of regular, nanometer-sized template by microwave assisted hydro- or solvo-thermal treatment of polymer films coated on surfaces followed by (2) coating of a layer of metal, metal oxides, polymers and inorganic materials. The nanometer-sized polymer template could be removed to create regularly shaped, hollow nanostructures (e.g., nano-bottles, nano-bowls, nano-holes etc.).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 60/831,194, filed Jul. 17, 2006 in the name of King Lun Yeung et al. and entitled “Method for Preparing Nanotextured Surfaces and Applications Thereof”, said provisional application being hereby incorporated by reference as if fully set forth herein.

FIELD OF THE INVENTION

The present subject matter relates to a method for creating a nanotextured surface using microwave-assisted irradiation. In particular, the present subject matter relates to a rapid and convenient method for creating a nanotextured surface involving transforming a polymer film on a substrate into uniform islands of a regularly shaped, nanometer sized template by microwave-assisted hydro- or solvo-thermal treatments of the polymer films.

BACKGROUND OF THE INVENTION

The fabrications of functional nanoarchitectures with the desired dimensional structure are of great importance because of their unique optical, electrical, magnetic and catalytic properties and have huge potential applications in electronics, sensors, optics, medicines, environments and chemical manufacturings. Current methods use traditional photolithograph, as well as more advanced soft-lithography and microfluidic techniques to shape microstructures from submicron to millimeter length scales. Except for the scanning probe microscope-based nanolithography (i.e., tip induced oxidation, dip-pen, nanografting) and biological-based assembly (i.e., molecular crossing and antibody-antigen recognition mechanisms), most of the nanometer-sized constructions were built via template-assisted and/or self-assembly procedures using molecules, clusters and particles as fundamental building blocks. The common templates used to prepare nanoscaled and nanotextured materials include patterned photoresists, polymer beads and surfactant molecules and the templates employed either top-down lithographic approach or bottom-up, self-assembly procedure.

Techniques for making nanostructured functional materials based on a polymer template have been reported in literature and patent application publications.

The most popular method for making nanostructured functional materials employs block polymer consisting of two or more different polymer chains (or blocks) that can spontaneously self-organize into nanometer-scale domains. The selective processing of one of the polymer chains or blocks using reactive ion etching has been used to produce periodic arrays at nanoscale. This method has been reported in: “Block copolymer Lighography: Periodic Arrays of ˜10¹¹ holes in a 1 Square Centimeter” Miri Park, et. al, Science 276 (1997) pp 1401-1404; “Nanoscale patterning using self-assembled polymer for semiconductor applications”, K. W. Guarini, et. al, J. Vac. Sci. Technolo. B 19(6) (2001) pp 2784-2788; “Process integration of self-assembled polymer templates into silicon nanofabrication”, K. W. Guarini, et. al, J. Vac. Sci. Technolo. B 20(6) (2002) pp 2788-2792; “Nanostructure fabrication using block copolymer”, I W Hamley, Nanotechnology 14 (2003) pp R39-R54.

In addition, U.S. Patent Application Publication No. 2006/0134556 to Paul F. Nealey et al. describes a method for replicating substrate patterns including patterns containing irregular features. This method involves depositing block copolymer materials on a patterned substrate and ordering components in the materials to replicate the pattern. Likewise, U.S. Patent Application Publication No. 2006/0078681 to Hiroyuki Hieda et al. describes a pattern forming method using phase separation structure of self-assembling block copolymer and minimizing variations in pattern. A substrate having groove structure pre-formed thereon, is coated with a solution of the block copolymer comprising at least one block having a mesogen group. The block copolymer is caused to self-assemble in the groove to form block copolymer assemblies, which are regularly arrayed.

In an alternate approach, polymer beads are assembled to form an ordered monolayer and multi-layers on surfaces onto which a deposition can be made. Inorganic oxides with ordered nanoporous structure prepared by this method have been reported in: “A simple Method for the production of a Two-Dimensional, Ordered Arrays of Small Latex Particles”, R. Micheletto, et. al, Langmuir 11 (1995) pp 3333-3336; “Large-Scale Fabrication of Ordered Nanobowl Arrays”, Xu Dong Wang, et. al, Nano letters 4 (11) (2004) pp 2223-2226”; “Large-Size Liftable Inverted-Nanobowl Sheets as Reusable Masks for Nanolithiography”, Xu Dong Wang, et. al, Nano Letters 5 (9) (2005) pp 1784-1788”; “Direct Growth of Mono- and Multilayer Nanostructured Porous Films on Curved surfaces and Their Application as Gas Sensors”, Fengqiang, Sun, et. al, Adv. Mater. 17 (2005) pp 2872-2877”.

Besides inorganic oxides, metals, carbon nanotubes, semiconductors and other materials were also prepared. This technology has been reported in: “Nanosphere lithography: A Versatile Nanofabrication Tool for Studies of Size-Dependent Nanoparticle Optics”, Christy L., et. al, J. Phy. Chem. B 105 (2001) pp 5599-5611; “Large-scale, 2D arrays of magnetic nanopaticles”, J. Rybczynski, et. al, Colloids and Surfaces A: Physicochem. Eng. Aspects 219 (2003) pp 1-6; “Photonic Crystalls Based on Periodic Arrays of aligned Carbon Nanotubes”, K. Kempa, et. al, Nano letters 3 (1) (2003) pp 13-18; “Large-scale Hexagonal-Patterned Growth of aligned ZnO Nanorods from Nano-optoelectronics and Nanosensor Arrays”, Xu Dong Wang et. al, Nano letters 4 (3) (2004) pp 423-426.

The high cost of preparing monodispersed polymer beads, however, made this approach an expensive method. Moreover, it is difficult to obtain regular monolayer coverage for polymer beads smaller than 50 nm.

An approach to use hydrothermal treatment to nanostructured films is described in U.S. Pat. No. 6,787,198 to Shyama P. Mukherjee et al. This patent describes a method involving the hydrothermal treatment of nanostructure films to form high k PMOD™ films for use in applications that are temperature sensitive, such as applications using a polymer based substrate. The patent does not use microwave irradiation.

Although Sridhar Komarneni discloses in Current Science, Vol. 85 No. 12, December 2003, that the use of microwave field during hydrothermal and solvothermal conditions dramatically enhances their crystallization rate, oxide materials such as zirconia, titania and various spinel ferrites and metals such as Pt, Pd, Ag, Au, etc. of different sizes and shapes were crystallized using the hydrothermal, microwave-hydrothermal and microwave-solvothermal methods.

Accordingly, there has been a need to develop a cost-effective, rapid and convenient method for creating a nanotextured surface.

SUMMARY OF THE INVENTION

The procedure of fabrication of polymer nanostructure in the present subject matter is prepared in not more than 15 minutes and the cost is very low. Further, the method of the present subject matter can be applied to semiconductor materials used on electronic devices, LCD and lighting; biomolecule immobilization, molecular storage and delivery for application in medicine, biotechnology, life-sciences, personal care products and cosmetics; surface coatings and protections; nanostructured magnetic devices for data storage and retrieval; and germicidal materials and coatings.

Accordingly, in one aspect of the present subject matter, a method for creating a nanotextured surface is provided, which comprises transforming a polymer film on a substrate into uniform islands of a regularly shaped, nanometer sized template by microwave irradiation. The microwave irradiation in the method is a microwave-assisted hydro- or solvo-thermal treatment.

In another aspect of the present subject matter, a method for creating a nanotextured surface is provided which comprises (a) providing a polymer film on a substrate; (b) transforming the polymer film into uniform islands of a regularly shaped, nanometer sized template by microwave irradiation, and (c) depositing materials onto the template. The microwave irradiation is a microwave-assisted hydro- or solvo-treatment achieved in the presence of a solvent, selected from the group consisting of water, alcohol, ketone and mixtures thereof.

Under microwave irradiation and heating, the polymer film rapidly transformed into uniform islands of nanometer-sized polymer islands. Polymethyl methacrylic (PMMA), polystyrene-polybutadiene-polystyrene (SBS) and SU-8 photoresist films are irradiated with microwave in water to form nanotextured surfaces comprising regular, nanometer-sized polymer islands. A thin coating can be deposited by either physical or chemical deposition methods, thereby creating a nanotextured surface made of desired materials.

In another aspect of the present subject matter, the method further comprises removing the polymer template to create a regularly shaped, hollow nanostructure. The nanostructures include without limitation nano-bottles, nano-bowls, nano-rings and nano-holes.

Nano-bottles are hollow semi-spheres with a tiny nanometer-sized hole for mouth. SiO₂ and TiO₂ nano-bottles are prepared by spin-coating a thin layer of SiO₂ or TiO₂ sol onto a PMMA nanostructured pattern followed by removal of the polymer by ozone oxidation or air calcination. The methodology is not limited to the use of SiO₂ or TiO₂ and the present disclosure contemplates the use of metals, metal oxides, semiconductor materials, carbon and other polymers within the methodology. The bottle mouth is created by an eruption caused by the gasification of the polymer.

Nano-bowls are obtained by chemical etching of the nano-bottles to create a larger opening. SiO₂ and TiO₂ nano-bottles are etched with acid or base etchants.

Nano-rings are prepared by removal of the polymer template by oxygen plasma at 473 K. SiO₂ or TiO₂ nano-rings are created during the oxygen plasma treatment.

Thin films with nanoholes are obtained by depositing a layer thickness similar or slightly thicker than the height of the polymer template. TiO₂ film with regular nanometer-sized holes is made by this procedure after annealing the film at 933 K.

The nano-bottle, nano-bowl, nano-ring and nano-hole structures can be used as a template for patterning the underlying substrate. Silicon with regular nanometer-sized holes is prepared using a two-step etching of SiO₂ nano-bottles deposited on silicon serving as pattern mask. The hollow structures are also useful as a template for the deposition and growth of a different material, for example, electroplating of metal within the hollow volume, deposition of polymer materials, carbon nanotubes (CNT) and so forth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an Atomic Force Microwave (AFM) image of PMMA thin film spin-coated on a clean silicon wafer before microwave treatment.

FIGS. 2( a) and (b) are AFM height and 3-D images of PMMA nanostructure with diameter of 83 nm and height of 38 nm produced according to the subject matter.

FIGS. 3( a) and (b) are AFM height and 3-D images of PMMA nanostructure with diameter of 63 nm and height of 28 nm produced according to the subject matter.

FIGS. 4( a) and (b) are AFM height and 3-D images of PMMA nanostructure with diameter of 59 nm and height of 24 nm produced according to one embodiment of the present subject matter.

FIGS. 5( a) and (b) are AFM height and 3-D images of PMMA nanostructure with diameter of 48 nm and height of 19 nm produced according to the subject matter.

FIGS. 6( a) and (b) are AFM height and 3-D images of PMMA nanostructure with diameter of 41 nm and height of 18 nm produced according to the subject matter.

FIGS. 7( a) and (b) are AFM height and 3-D images of PMMA nanostructure with diameter of 26 nm and height of 6 nm produced according to the subject matter.

FIG. 8 illustrates the changes of the diameter of the PMMA nanostructure according to one embodiment of the present subject matter with varying PMMA film thickness.

FIG. 9 illustrates the changes of the height of the PMMA nanostructure in accordance with the subject matter with varying PMMA film thickness.

FIG. 10 illustrates the changes of the density of the PMMA nanostructure according to one embodiment of the present subject matter with varying PMMA film thickness.

FIG. 11 is a Scanning Electron Microscopy (SEM) image of the PMMA nanostructure.

FIGS. 12( a) and (b) are AFM height and 3-D images of SBS nanostructure produced according to one embodiment of the present subject matter.

FIGS. 13( a) and (b) are AFM height and 3-D images of SU-8 nanostructure produced according to one embodiment of the present subject matter.

FIGS. 14( a) and (b) show the preparation of TiO₂ nanotextured surface according to one embodiment of the present subject matter, where (a) shows the PMMA nanostructure pattern before TiO₂ coating and (b) shows the surface structure after spin-coating a thin TiO₂ film on the pattern.

FIGS. 15( a) and (b) show the preparation of SiO₂ nanotextured surface according to one embodiment of the present subject matter, where (a) shows the PMMA nanostructure pattern before SiO₂ coating and (b) shows the surface structure after spin-coating a thin SiO₂ film on the pattern.

FIG. 16( a), (b), (c) and (d) show TiO₂ surface structure with and without nanotextured PMMA template according to one embodiment of the present subject matter, where (a) and (b) show the nanotextured TiO₂ with hollow, nano-bottle features obtained after ozone treatment at 473 K using nanotextured PMMA pattern as template, (c) and (d) show a similar TiO₂ film surface coated directly on the silicon wafer.

FIG. 17 shows the XPS measurement on the nanotextured TiO₂ surface with nano-bottle features according to one embodiment of the present subject matter.

FIG. 18( a), (b), (c) and (d) show TiO₂ surface structure with and without nanotextured PMMA as template according to one embodiment of the present subject matter, where (a) and (b) show the nanotextured TiO₂ with hollow, nano-bottle features obtained after air calcination at 723 K using nanotextured PMMA pattern as template, (c) and (d) show a similar TiO₂ film surface coated directly on the silicon wafer.

FIGS. 19( a) and (b) relate to Example 21 and show the nanotextured SiO₂ with hollow, nano-bottle features with a thinner shell after ozone treatment at 423 K.

FIGS. 20( a) and (b) relate to Example 22 and show the nanotextured SiO₂ with hollow, nano-bottle features with a thicker shell after ozone treatment at 423 K.

FIGS. 21( a) and (b) relate to Example 22 and show the nanotextured SiO₂ with hollow, nano-bottle features with a thicker shell after air calcination at 723 K.

FIG. 22 shows the nanotextured SiO₂ with hollow, nano-bowl features with a mouth diameter of 34 nm according to one embodiment of the present subject matter.

FIG. 23 shows the nanotextured SiO₂ with hollow, nano-bowl features with a mouth diameter of 87 nm according to one embodiment of the present subject matter.

FIG. 24 shows TiO₂ nano-ring feature after oxygen plasma treatment according to one embodiment of the present subject matter.

FIG. 25( a), (b), (c) and (d) show TiO₂ surface structure with and without nanotextured PMMA as template according to one embodiment of the present subject matter, where (a) and (b) show the TiO₂ film with nano-hole features obtained after air calcination at 933 K using nanotextured PMMA pattern as template, (c) and (d) show a similar TiO₂ film surface coated directly on the silicon wafer.

FIG. 26 shows Si nano-holes with diameter of 20 nm was obtained after two-step etching SiO₂ nano-bottles in KOH solutions according to one embodiment of the present subject matter.

FIG. 27 summarizes the procedures for preparing nano-bottle, nano-bowl, nano-ring and nano-hole structures.

FIG. 28 shows contact angle of water droplet on TiO₂ film.

FIG. 29 shows contact angle of water droplet on TiO₂ film with nanotextured SBS layer.

FIG. 30 shows contact angle of water droplet on TiO₂ film with nanotextured SBS layer.

FIGS. 31 (a) and (b) show fluorescent signal from BSA-FITC immobilized on SiO₂ nano-bowls, as compared to that of a flat SiO₂ film in FIGS. 31( c) and (d).

DETAILED DESCRIPTION OF THE INVENTION

Reference will not be made in detail to specific step by step embodiments of the present subject matter. Examples of the specific embodiments are illustrated in the accompanying drawings. While the subject matter will be described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the subject matter to such specific embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the subject matter. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present subject matter.

The present subject matter may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present subject matter.

The methods of the present subject matter result in nanotextured surfaces that exhibit many advantages. These advantages include the use as a mask for other nanostructures. The methods also change the surface properties and are used to manipulate the properties for better wetting, adhesion and roughness.

1. Preparation of Nanometer-Sized Polymer Template

In one aspect, the present subject matter provides a method for creating a nanotextured surface comprising transforming a polymer film on a substrate into uniform islands of regularly shaped, nanometer-sized polymers by microwave assisted hydro- or solvo-thermal treatments. The method involves (1) providing a polymer film on a substrate by deposition; and (2) transforming the polymer film into uniform islands of a regularly shaped, nanometer sized polymer template by microwave irradiation in the presence of a solvent, preferably water, alcohol, ketone or a mixture thereof. The film thickness is controlled by the coating process; and the microwave radiation dosage is adjusted by its irradiation power and time. A method of providing a polymer film on a substrate is accomplished by deposition using spin-coating.

Spin-Coating of a Polymer Film on a Substrate

A clean substrate, preferably a silicon wafer, is used as a substrate on which a polymer film is deposited. A silicon wafer is cut into small pieces such as, for example, 1×1 cm pieces. The diced wafers are ultrasonicated and cleaned in a solution at a proper temperature for the wafers, and then, rinsed in water and dried.

The polymer to be used may be any polymer without any particular limitation so long as it can be deposited to a substrate, preferably a silicon wafer and be transformed into uniform islands of regularly shaped, nanometer sized template by microwave irradiation. Non-limiting examples of usable polymer include a thermoplastic polymer such as PMMA, a block polymer such as SBS and a photoresist such as SU-8. A thermoplastic PMMA, a block polymer SBS and SU-8 photoresist are preferred for the present subject matter. In addition, resins are useful in this present methodology.

The polymer can be deposited on the silicon wafer by a conventional method, preferably by spin-coating method. PMMA with different molecular weights can be dissolved in a proper solvent, for example, such as chlorobenzene and spin-coated on a flat substrate using a proper device such as Speciality coating system, Inc., Model, P-6204, at different rotation speeds to obtain uniform PMMA film coatings of known thicknesses. The PMMA concentration and rotation speed controls the thickness of the spin coated films. Similarly, SBS with different molecular weights are dissolved in toluene and spin-coated on a flat substrate at different rotation speeds to obtain uniform SBS films coating of known thicknesses. SBS concentration and rotation speed controls the thickness of the spin coated films.

The spin-coated polymer films are outgassed at room temperature to remove the solvent used. The thickness of the film is determined by a conventional method and Ellipsometric Thin Film Thickness Measurement System (L116C, Gaertner) is used in the present subject matter. The spin-coated polymer films obtained are imaged using AFM (Digital Instruments, Nanoscope IIIa). FIG. 1 shows an AFM picture of a PMMA film spin-coated on a silicon wafer.

Microwave Assisted Irradiation of the Polymer Film

The second step of the method according the present subject matter involves transforming the polymer film into uniform islands of a regularly shaped, nanometer sized polymer template by microwave irradiation in the presence of a solvent.

The microwave irradiation is preferably microwave-assisted hydro- or solvo-thermal treatment. Microwave-assisted hydro- or solvo-thermal methods are low temperature treatments for the preparation of nanophase materials of different sizes and shapes. These methods save energy and are environmentally benign because the reactions take place in closed system conditions. The nanophase materials can be produced in either a batch or continuous process using the above methods. Microwave-assisted hydro- or solvo-thermal treatments, where the advantages of both microwave and hydro- or solvo-thermal methods are being made use of, may be carried out using a MARS-5 acid digestion system where reactants are treated in Teflon liners. Both temperature (maximum temperature of 240° C.) and/or pressure (maximum pressure of 350 psi) are precisely controlled with this system. The MARS 5 system uses 2.45 GHz frequency and has a maximum power of 1200 W. The power of this unit can be controlled from 0 to 100%.

Under microwave irradiation and heating, the polymer film is rapidly transformed into uniform islands of nanometer-sized polymer islands. Several parameters affect the size and shape of the polymer islands. These includes (a) nature of the polymer materials (i.e., chemical composition, molecular weight, purity) and its (b) glass transition and (c) melting point temperatures as well as its (d) adhesion strength on the substrate and (e) interactions with the solvent(s). For a fixed set of polymer, solvent(s) and substrate, the size of the polymer islands is directly dependent on (f) film thickness, (g) microwave irradiation energy and (h) irradiation time.

In one embodiment of the present subject matter, the spin-coated polymer film, preferably with a molecular weight of 25,000, is outgassed to remove the solvent. The outgassed sample is placed in a Teflon vessel and a solvent(s) such as water, alcohol, ketone or a mixture thereof is added. The vessel is irradiated with microwave radiation at an optimum dosage including irradiation power and time.

PMMA film, SBS film and SU-8 photoresist film are preferably irradiated with microwave in water to form nanotextured surfaces comprising regular, nanometer-sized polymer islands. For a PMMA film, the microwave treatment is preferably at a microwave power of 20-200 W and an irradiation time of 5 minutes to 2 h. For an SBS film and an SU-8 photoresist film, the microwave treatment is preferably at a microwave power of 20-200 W and an irradiation time of 5 minutes to 1 h.

After the irradiation, the vessel is cooled and the polymer film formed on the surface of the substrate is rinsed and dried. The film morphology of the sample is imaged using an AFM. Independent analysis is also made using a scanning electro-microscopy (SEM, JEOL 6700F).

AFM pictures taken after the irradiation show that regularly nanometer-sized polymer islands are uniformly distributed over the entire surface. In one embodiment of the present subject matter, a PMMA coated silicon surface having the polymer islands uniformly distributed over the entire surface was obtained after the microwave irradiation treatment (see FIG. 14( a) according to Example 17). The size of the polymer islands may be adjusted from as small as 10 nm to as big as 200 nm by adjusting the film thickness and microwave irradiation.

2. Preparation of Nanotextured Surface

In another aspect of the present subject matter, a method for creating a nanotextured surface comprises (a) providing a polymer film on a substrate; (b) transforming the polymer film into uniform islands of a regularly shaped, nanometer-sized template by microwave irradiation; and (c) depositing materials on the template. Materials that are useful for deposition or the template include materials selected from the group consisting of molecules, clusters and particles of metal, inorganic oxides, semiconductor and polymers. The materials are deposited onto the regularly shaped, nanometer-sized polymer islands prepared by microwave irradiation of deposited polymer films. Nanotextured surfaces are prepared from the deposited materials.

Colloidal TiO₂ or SiO₂ sol can be deposited onto the nanotextured polymer surface by spin coating. The thickness of the deposited TiO₂ or SiO₂ depends on the sol concentration and rotation speed. The titanium dioxide sol is obtained by hydrolysis of titanium isopropoxide in water-alcohol solution followed by peptization with acid. The silicon dioxide sol is obtained by hydrolysis of tetraethyl orthosilicate in water-alcohol solution followed by peptization with acid under reflex. Each sol preparation is conducted in nitrogen atmosphere to prevent uncontrolled precipitation of titanium oxide or silicon oxide. Further, the sol is centrifuged to remove coarse particles.

Spin-coating a dilute TiO₂ or SiO₂ sol at high rotation speed coats the polymers with a thin layer of TiO₂ or SiO₂ as shown in FIG. 14( b) and FIG. 15( b). X-ray photoelectron spectroscopy (XPS, Physical Electronics PHI 5600) may be used to determine the surface chemical composition. The sample is mounted on a holder and placed in the XPS chamber. The sample is outgassed at ultrahigh vacuum and irradiated with monochromatic AlKα X-ray. XPS analysis indicates that spin coating uniformly coated TiO₂ or SiO₂ on the entire surface of the sample.

3. Preparation of Hollow Nanostructure

In another aspect, the present subject matter provides a method for creating a nanotextured surface further comprising the step of removing the polymer template to create a regularly shaped, hollow nanostructure. Hollow nanostructures are obtained upon removal of the polymer template after the deposition of metal, inorganic oxides, semiconductor and polymer films on the regularly shaped, nanometer-sized polymer islands prepared by microwave irradiation of deposited polymer films. The regularly shaped, hollow nanostructure may be any of nano-bottles, nano-bowls, nano-rings and nano-holes.

Nano-bottles are hollow semi-spheres with a tiny nanometer-sized hole for mouth. SiO₂ or TiO₂ nano-bottles are prepared by spin-coating a thin layer of SiO₂ or TiO₂ sol onto a PMMA nanostructured pattern followed by removal of the polymer by ozone oxidation at 473 K or air calcination at 723 K. The bottle mouth is created by an eruption caused by the gasification of the polymer.

A thin layer of TiO₂ or SiO₂ film may be coated onto the nanotextured polymer surface by spin coating from a dilute colloidal TiO₂ or SiO₂ sol, preferably 0.05 mol/L TiO₂ or SiO₂ to prepare a nanotextured SiO₂ surface with nano-bottles. Likewise, a thicker lay of SiO₂ film may be coated onto the nanotextured polymer surface by spin coating from a colloidal TiO₂ or SiO₂ sol, preferably 0.25 mol/L TiO₂ or SiO₂ sol to prepare a thicker nanotextured SiO₂ surface with nano-bottles. The TiO₂ or SiO₂ shell obtained by the thicker layer is thicker as the spin-coated TiO₂ or SiO₂ layer is thicker. In either case, the polymer film is removed by a gas phase oxidation and a uniform TiO₂ or SiO₂ coverage is obtained.

Any conventional method may be used for the removal of the polymer film. Ozone oxidation, oxygen plasma or calcination is preferably used for the present subject matter. The sample may be placed under 250 sccm of 100 g/m³ O₃ in O₂ gas mixture at 473 K to 723 K. The sample is then imaged using AFM to image the film morphology. FIGS. 16( a) and (b) and FIGS. 18( a) and (b) show a TiO₂ nanotextured surface that consists of nano-bottle features, i.e., a semi-sphere with a narrow hole at the top; and FIGS. 19( a) and (b), FIGS. 20( a) and (b) and FIGS. 21( a) and (b) show SiO₂ nanotextured surface that comprises nano-bottle features. It can be seen from the figures that the nano-bottles have uniform sizes and cover the entire area of the sample.

Nano-bowls are obtained by chemical etching of the nano-bottles to create a larger opening. SiO₂ or TiO₂ nano-bottles may be etched with acid or base etchants, turning the nano-bottles into nano-bowls. The size of the opening is controlled by the etching time. The sample is imaged using AFM (Digital Instruments, Nanoscope IIIa) and X-ray photoelectron spectroscopy (XPS, Physical Electronics PHI 5600) is used to determine the surface chemical composition. FIGS. 21, 22 and 23 show, respectively, SiO₂ nano-bottles with a different bottle mouth from 16 nm to 87 nm, obtained under different etching time of from 0 to 170 minutes.

Nano-rings or nano-corrals are prepared by removal of the polymer template by oxygen plasma at 473 K. SiO₂ or TiO₂ nano-rings are created during the oxygen plasma treatment step. The sample is imaged using AFM (Digital Instruments, Nanoscope IIIa) and X-ray photoelectron spectroscopy (XPS, Physical Electronics PHI 5600) is used to determine the surface chemical composition.

Thin films with nanoholes are obtained by depositing a layer with thickness similar or slightly thicker than the height of the polymer template. TiO₂ film with regular nanometer-sized holes is made by this procedure after annealing the film at 933 K. A shorter time has proven effective, but a longer time is preferably used to anneal the film. FIGS. 25( a) and (b) show a TiO₂ film with nano-holes and FIGS. 25( c) and (d) show the surface feature of a similarly prepared TiO₂ film spin-coated on silicon for comparison. It can be seen from the figures that the nano-holes have uniform sizes and cover the entire area of the sample. From the comparison, it is clear that the nano-holes are the result of the preparation procedure described in this disclosure.

The nano-bottle, nano-bowl, nano-ring and nano-hole structures may be used as a template for patterning the underlying substrate. Silicon with regular nanometer-sized holes is prepared using a two-step etching of SiO₂ nano-bottles deposited on a silicon serving as pattern mask with acid or base, to enlarge the opening mouth of the nano-bottles and etch the silicon beneath. FIG. 26 shows a silicon sample uniformly etched with 20 nm nano-holes.

FIG. 27 summarizes the procedures for preparing nano-bottle, nano-bowl, nano-ring and nano-hole structures.

4. Applications of Nanotextured Surfaces

Self-Cleaning, Germicidal Surface Coating

A self-cleaning, germicidal surface coating combining the self-cleaning properties of lotus-leaf effect (i.e., superhydrophobicity) and germicidal properties of TiO₂-based coating could be prepared according to this disclosure. Applications include indoor and outdoor surface protection coating, appliance and equipment coating, kitchenwares, toiletwares, glasses, mirrors, tiles, toilet bowls and seats, sinks and furniture. Self-cleaning, germicidal surface coating will also be useful for exterior and interior coatings for vehicles including cars, trains, boats, planes and others. FIG. 28 shows the well known superhydrophilic property of a TiO₂ thin film. Water placed on TiO₂ thin film has a contact angle of 0 and spreads even over the surface. Although useful in many applications, this property tends to also spread germs and bacteria over the entire surface. FIG. 29 shows a similar TiO₂ coated surface coated with nanotextured SBS. The contact angle of the water droplet was increased to ˜100° making the surface hydrophobic and preventing the spread of contaminated liquid droplets over the entire surface. FIG. 30 shows a similar TiO₂ coated surface coated with nanotextured SBS. The contact angle of the water droplet was increased to >1000 making the surface superhydrophobic. This allows the droplet to freely flow away from the surface (i.e., lotus-leaf effects), while minimizing surface contact with the contaminated liquid droplets.

Nanotextured Polymer Surfaces for LCD and Lighting

Nanotextured surfaces have application for liquid crystal display (LCD) and lighting. The nanotextured polymers obtained according to one embodiment of the present subject matter may be used to pre-set the tilt angle for LCD enabling better display performance. Coating anatase TiO₂ or rutile TiO₂ nanoparticles onto the nanotextured polymers according to one embodiment of the present subject matter may enhance lighting performance for LCD. Similar or higher enhancement may be obtained by coating aligned carbon nanotubes.

Nanotextured Polymer Surfaces for Surface Coating

Nanotexturing of polymer changes their surface wetting properties. Superhydrophilic and superhydrophobic properties as described above may be designed by simply changing the size and shape of the polymer nanotexture. Applications include surface coatings and finishing, anti-corrosion coatings, non-stick surface, anti-stain coatings, anti-fogging coating and others.

Nanotextured TiO₂ Surface.

The nanotextured TiO₂ surfaces according to one embodiment of the present subject matter transform a superhydrophilic surface into a superhydrophobic surface. This allows the droplet to freely flow away from the surface (i.e., lotus-leaf effects), while minimizing surface contact with the contaminated liquid droplets. This results in a combined lotus-leaf effect and surface germicidal properties. Applications include indoor and outdoor surface protection coating, appliance and equipment coating, kitchenwares, toiletwares, glasses, mirrors, tiles, toilet bowls and seats, sinks and furniture. Self-cleaning, germicidal surface coating will also be useful for exterior and interior coatings for vehicles including car, trains, boats, planes and others.

Immobilization of Biomolecules in SiO₂ Nano-Bowls.

Immobilization of biomolecules (e.g., proteins, enzymes, DNA, cells) is important for drug screening, medical diagnosis, DNA chips and Bio-MEMS. As tested in the present disclosure (Example 29), the increased fluorescent signal shown in FIG. 31 for BSA-FITC immobilized on SiO₂ nano-bowls indicates the successfully immobilization of the BSA biomolecules in contrast to that of the non-textured surface.

Storage in Nano-Bottles

Chemicals including drugs, reagents, fragrances and germicides may be stored in the nano-bottles for controlled or programmed released for applications in sensor, medicine, cosmetic and personal-care products.

Odor Removal and Adsorption in Inorganic Oxide Nano-Bottles

The TiO₂ and SiO₂ nano-bottles are able to adsorb molecules and could be used to remove malodor from the environment.

Inorganic Oxide Nano-Holes

The TiO₂, SiO₂ and Si nano-holes according to one embodiment of the present subject matter (Examples 26 and 27) have applications as nanoporous membranes for molecular separation and sensor barriers. They also have uses in microelectronic and microelectromechanical systems.

EXAMPLES

The embodiment of the present subject matter will be described below in further detail with reference to the examples, but the present subject matter is not intended to be limited to these examples.

In the examples, the thickness of the film obtained was determined by an Ellipsometric Thin Film Thickness Measurement System (L116C, Gaertner).

Further, the samples obtained were imaged using AFM (Digital Instruments, Nanoscope IIIa). A piezoelectric scanner (type J) with a scan size of 125×125 μm² and a vertical movement of 5 μm was used to image the film morphology.

Further, X-ray photoelectron spectroscopy (XPS, Physical Electronics PHI 5600) was used to determine the surface chemical composition. The sample was mounted on a holder and placed in the XPS chamber. The sample was outgassed at ultrahigh vacuum and irradiated with monochromatic AlKα X-ray.

Example 1 Preparation of a Silicon Wafer

A silicon wafer (Si(100) wafer) was cut into 1×1 cm pieces. The diced wafers were ultrasonicated in acetone followed by ethanol and Distilled deionized (DDI) water for 30 minutes each. The wafers were further cleaned in a 2H₂SO₄:H₂O₂ solution at 353 K for 20 minutes before a final rinse in DDI water and drying in an oven.

Example 2 Preparation of PMMA Solution

1.32 g of PMMA (Polysciences, Inc) with an average molecular weight of 25,000 g/mol was added into 18.02 ml of chlorobenzene (Merck-schuchardt) solution under vigorous stirring at 373 K until a completely transparent solution of PMMA was obtained. The concentration of the as-prepared PMMA solution was 73.70 mg/ml.

Example 3 Preparation of SBS Solution

300 mg of SBS (Finaprene) was added into 10 ml of toluene (Aldrich) solution under vigorous stirring condition at 403 K until a completely transparent solution of SBS was obtained. The concentration of the as-prepared SBS solution was 30 mg/ml.

Example 4 Preparation of SBS Solution

10 mg of SBS (Finaprene) was added into 10 ml of toluene (Aldrich) solution under vigorous stirring at 403 K until a completely transparent solution of SBS was obtained. The concentration of the as-prepared SBS solution was 1 mg/ml.

Example 5 Spin-Coating of PMMA Solution

0.022 g of PMMA (Polysciences, Inc) with an average molecular weight of 25,000 g/mol was added into 18 ml of chlorobenzene (Merck-schuchardt) solution under vigorous stirring at 373 K until a completely transparent solution of PMMA was obtained. The concentration of the as-prepared PMMA solution was 1.23 mg/ml. Using a spin-coating device, Speciality Coating System, Inc., Model, P-6204, 30 μl of the PMMA solution obtained was deposited at 2000 rpm for 60 seconds on the silicon wafer prepared according to Example 1. An AFM picture of the spin-coated PMMA film obtained is shown in FIG. 1.

Examples 6-11 Spin-Coating of PMMA Solutions

Using the same preparation method as described in Example 2, except for the concentration of PMMA solution and the rotation speed, various PMMA solutions were prepared. 30 μl of each PMMA solution was deposited on the silicon wafer prepared according to Example 1 using a spin-coating device, Speciality Coating System, Inc., Model, P-6204, as follows:

Example 6

30 μl of 1.23 mg/ml PMMA/chlorobenzene spin-coated at 2000 rpm;

Example 7

30 μl of 1.23 mg/ml PMMA/chlorobenzene spin-coated at 4000 rpm;

Example 8

30 μl of 1.23 mg/ml PMMA/chlorobenzene spin-coated at 7000 rpm for 60 seconds;

Example 9

30 μl of 0.62 mg/ml PMMA/chlorobenzene spin-coated at 7000 rpm for 60 seconds;

Example 10

30 μl of 0.31 mg/ml PMMA/chlorobenzene spin-coated at 7000 rpm for 60 seconds;

Example 11

30 μl of 0.15 mg/ml PMMA/chlorobenzene spin-coated at 7000 rpm for 60 seconds;

The spin-coated PMMA films were outgassed at room temperature to remove the chlorobenzene solvent. The film thickness of each of the above samples was measured.

Example 12 Spin-Coating of SBS Solution

30 μl of 1 mg/ml SBS solution prepared according to Example 4 was spin-coated at 3000 rpm for 60 seconds on the silicon wafer prepared according to Example 1, using a spin-coating device, Speciality Coating System, Inc., Model, P-6204. The spin-coated SBS film was outgassed at room temperature to remove the toluene solvent. The film thickness of the film was measured.

Example 13 Spin-Coating of SU-8 Solution

SU-8 film was spin-coated on clean silicon wafer at a rotation speed of 1000 rpm and held at 4000 rpm for 30 seconds (Solite 5110-C/PD Wafer spinner). The SU-8 film was pre-baked on a hot plate at 338 K for 10 minutes followed by a soft bake at 368 K for 30 minutes before cooling to room temperature. The spin-coated SU-8 films were outgassed at room temperature to remove the solvent. The film thickness of the above samples was measured.

Example 14 Microwave-Assisted Hydrothermal Treatment of PMMA Films

The PMMA films prepared according to Examples 6-11 were transferred to a 100 ml Teflon lined vessel (MDR-1000/6/100/110) containing 50 ml of Distilled deionized (DDI) water. The Teflon vessel was placed in the microwave oven (MLS-1200 MEGA, MILESTONE) and irradiated with 60 W power for 15 minutes under constant rotation. After that, the vessel was cooled down and the samples were rinsed with DDI water and dried.

The AFM images were respectively displayed in FIGS. 2-7 for the effects of rotation speeds and PMMA concentrations after microwave-assisted irradiation: FIG. 2 shows the AFM image for the PMMA film according to Example 6 (i.e., 1.23 mg/ml PMMA/chlorobenzene spin-coated at 2000 rpm); FIG. 3 shows the AFM image for the PMMA film according to Example 7 (i.e., 1.23 mg/ml PMMA/chlorobenzene spin-coated at 4000 rpm); FIG. 4 shows the AFM image for the PMMA film according to Example 8 (i.e., 1.23 mg/ml PMMA/chlorobenzene spin-coated at 7000 rpm); FIG. 5 shows the AFM image for the PMMA film according to Example 9 (i.e., 0.62 mg/ml PMMA/chlorobenzene spin-coated at 7000 rpm); FIG. 6 shows the AFM image for the PMMA film according to Example 10 (i.e., 0.31 mg/ml PMMA/chlorobenzene spin-coated at 7000 rpm); FIG. 7 shows the AFM image for the PMMA film according to Example 11 (i.e., 0.15 mg/ml PMMA/chlorobenzene spin-coated at 7000 rpm).

Example 15 Microwave Assisted Hydrothermal Treatment of SBS Films

The SBS film prepared according to Example 12 was transferred to a 100 ml Teflon lined vessel (MDR-1000/6/100/110) containing 50 ml of distilled deionized (DDI) water. The Teflon vessel was placed in the microwave oven (MLS-1200 MEGA, MILESTONE) and irradiated with 60 W power for 15 minutes under constant rotation. The vessel was cooled down and the film sample was rinsed with DDI water and dried. The AFM image of the nanotextured surface prepared from the SBS film was shown in FIG. 12. A bimodal distribution consisting of 20 and 80 nm was observed.

Example 16 Microwave assisted hydrothermal treatment of SU-8 film

The SU-8 films were transferred to a 100 ml Teflon lined vessel (MDR-1000/6/100/110) containing 50 ml of distilled deionized (DDI) water. The Teflon vessel was placed in the microwave oven (MLS-1200 MEGA, MILESTONE) and irradiated with 60 W power for 15 minutes under constant rotation. The vessel was cooled down and the sample was rinsed and dried. FIG. 13 displays the AFM image of the nanotextured surface prepared from SU-8 film. An average size of 40 nm was obtained.

Example 17 Preparation of TiO₂ nanotextured surface

A 0.05 mol/L TiO₂ sol was spin-coated on a silicon surface with PMMA nanotexture at a 6000 rpm, using a spin-coating device (Speciality Coating System, Inc., Model, P-6204). After spin-coating the sample was outgassed at room temperature to remove the solvent. The sample was imaged using AFM. Spin-coating a dilute TiO₂ sol at high rotation speed coated the polymers with a thin layer of TiO₂ as shown in FIG. 14( b). FIG. 14( a) shows the PMMA coated silicon surface after the microwave irradiation treatment but before the TiO₂ spin-coating. XPS analysis indicated that spin coating uniformly coated TiO₂ on the entire surface of the sample.

Example 18 Preparation of SiO₂ Nanotextured Surface

A 0.05 mol/L SiO₂ sol in ethanol was spin-coated on a silicon surface with PMMA nanotexture at a 6000 rpm (Speciality Coating System, Inc., Model, P-6204). After spin-coating the sample was outgassed at room temperature to remove the solvent. The sample was imaged using AFM. Spin-coating a dilute SiO₂ sol at high rotation speed coated the polymers with a thin layer of SiO₂ as shown in FIG. 15( b). FIG. 15( a) shows the PMMA coated silicon surface after the microwave irradiation treatment but before the TiO₂ spin-coating. XPS analysis indicated that spin coating uniformly coated SiO₂ on the entire surface of the sample.

Example 19 Preparation of Nanotextured TiO₂ Surface with Nano-Bottles

The TiO₂ coated sample prepared according to Example 17 was placed in a reactor and heated to 473 K at 3 K/min. The polymer template was removed by 250 sccm of 100 g/m³ O₃ in O₂ gas mixture at 473 K for 5 to 6 h. The sample was cooled to room temperature and removed for analysis. The obtained AMF image of TiO₂ nanotextured surface that consists of nano-bottle features was shown in FIGS. 16( a) and (b). For comparison, the surface feature of a similarly prepared TiO₂ film spin-coated on silicon was shown in FIGS. 16( c) and (d). It made clear that the nano-bottles are the result of the preparation procedure according to the present subject matter. XPS analysis of the sample indicated a uniform TiO₂ surface coverage. FIG. 17 shows two peaks located around 459 and 465 eV belonging to Ti⁴⁺2p_(3/2) and 2p_(1/2).

Example 20 Preparation of TiO₂ Nano-Bottles

The TiO₂ coated sample prepared according to Example 17 was placed in a furnace and calcined in air at 723 K for 10 h. The sample was cooled to room temperature and removed for analysis. The sample was imaged using AFM. The obtained TiO₂ nanotextured surface that consists of nano-bottle features was shown in FIGS. 18( a) and (b). For comparison, the surface feature of a similarly prepared TiO₂ film spin-coated on silicon was shown in FIGS. 18( c) and (d). It made clear that the nano-bottles were the result of the preparation procedure according to the present subject matter. XPS analysis of the sample indicated a uniform TiO₂ surface coverage.

Example 21 Preparation of SiO₂ Nano-Bottles

The SiO₂ coated sample prepared according to Example 18 was placed in a reactor and heated to 473 K at 3 K/min. The polymer template was removed by 250 sccm of 100 g/m³ O₃ in O₂ gas mixture at 473 K for 5 to 6 h. The sample was cooled to room temperature and removed for analysis. The sample was imaged using AFM. The obtained SiO₂ nanotextured surface that consists of nano-bottle features was shown in FIGS. 19( a) and (b). XPS analysis of the sample indicated a uniform SiO₂ surface coverage. For comparison, the surface feature of a similarly prepared SiO₂ film spin-coated on silicon for comparison was shown in FIGS. 19( c) and (d). It made clear that the nano-bottles are the result of the preparation procedure according to the present subject matter.

Example 22 Preparation of SiO₂ Nano-Bottles with Thicker Shell

Using the same method as described in Example 21, except for the use of a thicker layer of SiO₂ coated sample which was prepared by spin-coating 0.25 mol/L SiO₂ sol onto the silicon wafer with PMMA nanotexture at a 6000 rpm, SiO₂ nanotextured surface that consists of nano-bottles with thicker shell was prepared as shown FIGS. 20 (a) and (b). The SiO₂ shell was thicker as the spin-coated SiO₂ layer was thicker. XPS analysis of the sample indicated a uniform SiO₂ surface coverage.

Example 23 Preparation of SiO₂ Nano-Bottles with Thicker Shell

0.25 mol/L SiO₂ sol was spin-coated on a silicon surface with PMMA nanotexture at a 6000 rpm (Speciality Coating System, Inc., Model, P-6204). After spin-coating the sample was outgassed at room temperature to remove the solvent. The SiO₂ coated sample was placed in a furnace and calcined in air at 723 K for 10 h. The sample was cooled to room temperature and removed for analysis. The sample was imaged using AFM. FIGS. 21 (a) and (b) show the obtained SiO₂ nanotextured surface that consists of nano-bottles with thicker shell. The SiO₂ shell was thicker as the spin-coated SiO₂ layer was thicker. XPS analysis of the sample indicated a uniform SiO₂ surface coverage.

Example 24 Preparation of SiO₂ Nano-Bowls

A 0.25 mol/L SiO₂ sol was spin-coated on a silicon surface with PMMA nanotexture at a 6000 rpm (Speciality Coating System, Inc., Model, P-6204). After spin-coating the sample was outgassed at room temperature to remove the solvent. The SiO₂ coated sample was placed in a furnace and calcined in air at 823 K for 10 h. The sample was cooled to room temperature and removed for analysis. The resulting SiO₂ nano-bottles were transformed into nano-bowls by etching in 10 wt. % KOH solution for 90 minutes and 170 minutes. The sample was imaged using AFM. SiO₂ nano-bottles with a bottle mouth of 16 nm were shown in FIG. 21. SiO₂ nano-bowls with a mouth of 34 nm obtained under etching time 90 minutes was shown in FIG. 22. SiO₂ nano-bowls with a mouth of 87 nm obtained under etching time of 170 minutes was shown in FIG. 23. XPS analysis of the sample indicated a uniform SiO₂ surface coverage.

Example 25 Preparation of TiO₂ Nano-Rings (Nano-Corrals)

A 0.05 mol/L TiO₂ sol was spin-coated on a silicon surface with PMMA nanotexture at a 6000 rpm (Speciality Coating System, Inc., Model, P-6204). After spin-coating the sample was outgassed at room temperature to remove the solvent. The TiO₂ coated sample was treated under oxygen plasma at 473 K for 30 minutes. The sample was imaged using AFM. The obtained TiO₂ nanotextured surface that consists of nano-ring features made of fused TiO₂ nanoparticles was shown in FIG. 24. XPS analysis of the sample indicated a uniform TiO₂ surface coverage.

Example 26 Preparation of TiO₂ Film with Nano-Holes

A 0.05 mol/L TiO₂ sol was spin-coated on a silicon surface with PMMA nanotexture at a 6000 rpm (Speciality Coating System, Inc., Model, P-6204). After spin-coating the sample was outgassed at room temperature to remove the solvent. The TiO₂ coated sample was placed in the furnace and calcined in air at 933 K for 10 h. The obtained TiO₂ film with nano-holes was shown in FIGS. 25( a) and (b). For comparison, a similarly prepared comparative TiO₂ film was shown in FIGS. 25( c) and (d). XPS analysis of the sample indicated a uniform TiO₂ surface coverage.

Example 27 Preparation of Silicon Etched with Regular Nano-Holes

A 0.25 mol/L SiO₂ sol was spin-coated on a silicon surface with PMMA nanotexture at a 6000 rpm (Speciality Coating System, Inc., Model, P-6204). After spin-coating the sample was outgassed at room temperature to remove the solvent. The SiO₂ coated sample was placed in the furnace and calcined in air at 823 K for 10 h to obtain SiO₂ nano-bottles. The sample was etched in two steps with 10 wt. % and 20 wt. % KOH solutions to first enlarge the opening mouth of the nano-bottles and etch the silicon beneath. The sample was imaged using AFM. FIG. 26 showed a silicon sample uniformly etched with 20 nm holes.

Example 28 Test for Self-Cleaning, Germicidal Surface Coating

0.20 M TiO₂ sol was coated on a glass surface and calcined in air at 773 K for 10 h. 30 μl of 30 mg/ml SBS/toluene was spin-coated on the TiO₂ coated glass and irradiated with microwave under hydrothermal conditions. X-ray diffraction and micro-Raman analyses were carried out and the results indicated that the TiO₂ coated on the glass is anatase with 10 nm particle size. Anatase TiO₂ possesses latent germicidal property that is enhanced upon exposure to UV light source (i.e., sunlight or UV lamp). Wetting angle measurements were conducted using water. As shown in FIG. 29 and FIG. 30, in the TiO₂ coated surface coated with nanotextured SBS, the contact angle of the water droplet was increased to ˜100° making the surface hydrophobic and to >100° making the surface superhydrophobic, respectively. It was compared with a well known superhydrophilic TiO₂ thin film as shown in FIG. 28 for comparison.

Example 29 Immobilization of Biomolecules in SiO₂ Nano-Bowls

SiO₂ nano-bowls were prepared according to the procedure described in Example 23 with the etching time adjusted to 30 minutes. The sample was incubated in 1 mg/ml fluorescent isothiocyanate labeled bovine serum albumin (BSA-FITC, Sigma) for 40 minutes before rinsing in a phosphate buffered solution for 30 minutes. The immobilized BSA-FITC was imaged by a fluorescent microscope (BX41, Olympus) at an excitation wavelength of 400-490 nm. The pictures were taken at 40× magnification with an exposure time of 2000 ms with the shutter fully open. The increase fluorescent signal seen in FIG. 31 for BSA-FITC immobilized on SiO₂ nano-bowls indicated the successfully immobilization of the BSA biomolecules in contrast to that of the non-textured surface. 

1. A method for creating a nanotextured surface, comprising (a) depositing a polymer film on a substrate; and (b) transforming the polymer film into uniform islands of a regularly shaped, nanometer sized template by microwave irradiation.
 2. The method of claim 1, wherein the microwave irradiation is a microwave-assisted hydro- or solvo-thermal treatment.
 3. A method for creating a nanotextured surface, which comprises (a) depositing a polymer film on a substrate; (b) transforming the polymer film into uniform islands of a regularly shaped, nanometer sized template by microwave irradiation; and (c) depositing at least one other material to the template.
 4. The method of claim 3, wherein the microwave irradiation is a microwave-assisted hydro- or solvo-treatment.
 5. The method of claim 3, which further comprises removing the polymer template to create a regularly shaped, hollow nanostructure.
 6. The method of claim 1, wherein the polymer film is selected from the group consisting of thermoplastic polymers, block polymers, resin and photoresists.
 7. The method of claim 1, wherein the polymer film is selected from the group consisting of Polymethyl methacryliate (PMMA), polystyrene-polybutadiene-polystyrene (SBS) and SU-8.
 8. The method of claim 1, the microwave irradiation is achieved in the presence of solvents.
 9. The method of claim 8, the solvents are selected from the group consisting of water, alcohol, ketone and mixture thereof.
 10. The method of claim 3, wherein the at least one other material is selected from the group consisting of molecules, clusters and articles of metal, metal oxides, semiconductors, polymers and inorganic materials.
 11. The method of claim 3, wherein the deposition results in a thin coating layer of about 3 nm to about 7 nm.
 12. The method of claim 11, wherein the coating layer is a thin coating layer of SiO₂ or TiO₂.
 13. The method of claim 12, wherein the SiO₂ or TiO₂ is coated onto the polymer template made from PMMA.
 14. The method of claim 1, wherein the islands have a size from about 10 nm to about 200 nm.
 15. The method of claim 4, wherein the regularly shaped, hollow nanostructure is any of nano-bottles, nano-bowls, nano-rings and nano-holes.
 16. The method of claim 15, wherein the regularly shaped, hollow nanostructure is nano-bottles.
 17. The method of claim 16, wherein the nano-bottles are SiO₂ or TiO₂ nano-bottles.
 18. The method of claim 17, wherein the nano-bottles are prepared by removing the polymer template by ozone oxidation.
 19. The method of claim 16, wherein the nano-bottle is further etched to obtain nano-bowls.
 20. The method of claim 19, wherein the nano-bowls are SiO₂ or TiO₂ nano-bowls.
 21. The method of claim 15, wherein the regularly shaped, hollow nanostructure is nano-rings.
 22. The method of claim 15, wherein the nano-rings are prepared by removing the polymer template by oxygen plasma.
 23. The method of claim 15, wherein the nano-holes are prepared by removing the polymer template by air carcination.
 24. The nanostructures prepared by the method of claim
 15. 